Technical Field
The present invention relates to an oriented flexible film material that can be used in products and to a method of making the oriented flexible film.
Description of Related Art
Multi-layered film structures are often used in flexible packages where there is a need for advantageous barrier, sealant, and graphics-capability properties. Barrier properties in one or more layers are important in order to protect the product inside the package from light, oxygen or moisture. Such a need exists, for example, for the protection of foodstuffs, which may run the risk of flavor loss, staling, or spoilage if insufficient barrier properties are present to prevent transmission of such things as light, oxygen, or moisture into the package. The sealant properties are important in order to enable the flexible package to form an airtight or hermetic seal. Without a hermetic seal, any barrier properties provided by the film are ineffective against oxygen, moisture, or aroma transmission between the product in the package and the outside. A graphics capability is needed because it enables a consumer to quickly identify the product that he or she is seeking to purchase, allows food product manufacturers a way to label the nutritional content of the packaged food, and enables pricing information, such as bar codes, to be placed on the product.
One prior art method of producing polymer films is the blown film extrusion process. Blown film is created by extruding molten polymer resin through an annular die. Gas is blown onto the polymer film ring to stretch it and create a bubble with expanded diameter. The bubble is then collapsed into a two-layer sheet by rollers, optionally slit, and wound onto a storage roller.
There are several disadvantages to using blown film in subsequent printing and packaging operations. Blown film suffers from imperfections in the rolling and winding processes, such as wrinkles and fold-overs, which make its use in printing and packaging uneconomical. Graphics printing processes require smooth, uniform surfaces to produce attractive and functional films. Blown film is also typically very thick as compared to films produced by other processes. Therefore, yield, which can be expressed in square inches per pound of polymer, is very low in blown film. Additionally, blown film can have low tensile strength as compared to other films.